Respirators are commonly provided with harnesses to support the mask body on a wearer's face during use. Some respirator harnesses are provided with a “drop-down” assembly that allows the mask body to be conveniently disposed beneath a wearer's chin when not in use. Occasions frequently arise in the workplace which require the respirator wearer to temporarily displace the mask body from their face when they are away from a contaminated area. The wearer may, for example, temporarily leave the contaminated area for a short time period to briefly speak to another person. To satisfy the need for easy mask body displacement and temporary-off-the-face storage beneath the chin, respirator designers have created these “drop-down” facemask assemblies for this purpose.
U.S. Pat. No. 6,715,490 to Byram discloses a drop-down respirator that has a head cradle or crown member and a pair of straps for supporting the mask body on the wearer's head. To provide temporary off-the-face storage, the Byram harness uses a substantially flat, flexible strap and an element that contains a curved elongated slot. When the flat strap is threaded through the curved elongated slot, the curved configuration of the slot causes the flat strap to be deformed into a curved configuration. This strap deformation allows it to frictionally engage the element, which in turn allows the respirator body to be incrementally withdrawn from the wearer's face so that it can be temporarily stored beneath the wearer's chin and can be conveniently repositioned over the nose and mouth by simply pulling on the free ends of each strap.
U.S. Pat. No. 6,732,733 to Brostrom et al. has a carriage that is disposed on the mask body and that is adapted for engaging the straps that are threaded through four spaced apart guide members on the carriage. The guide members cause the straps to take on a cross-configuration with respect to the four engagement points. This structure enables the mask body to be retained in a second position, dropped down beneath the face of the wearer, without removing the support harness from the wearer's head.
U.S. Pat. No. 6,497,232 to Fecteau et al. describes a quick-release mechanism and headpiece or crown member for use with the respirator. The headpiece is joined to a pair of straps for supporting the mask body on the wearer's head. The quick-release mechanism has a cam latch that is pivotally attached to a yoke to control the tension in an upward tension strap. In the latched position, the upper tension strap traverses the yoke to support and seal the respirator mask against the wearer's face. In the unlatched position, the upper tension straps loosely support the mask body below the chin of the wearer in a parked position. Fecteau et al. relies on the inclusion of a cam latch to move the mask from its in-use position to is parked position.
Thus, in the known drop-down harness assemblies described in the Byram, Brostrom et al., and Fecteau et al. patents, the crown members remain on the wearer's head while the mask body becomes dropped down beneath the chin.